This Keystone Symposium will focus on the rapidly expanding and topical field of mucosal inflammation and its regulation and will consider mechanisms of inflammation relative to all mucosal surfaces. A particular strength of this meeting is that it will be run jointly with a meeting on Hygiene, Allergy and Asthma, allowing a comprehensive examination of genetic, environmental and immune pathological factors involved in inflammation at different mucosal surfaces. In the first part of the Symposium factors that control the overall development of the mucosal immune system will be considered as well as the mechanism of tolerance induction in the mucosal immune system. These topics will provide the theoretical basis for the understanding of mucosal inflammation. Next there will be a plenary session held jointly with the "sister" Symposium that will focus on dendritic cell function in the gastrointestinal and pulmonary tracts followed by an examination of effector and regulatory mechanisms underlying mucosal inflammation. In the latter half there will be a second joint plenary session in this case considering regulatory (suppressor) mechanism in the gastrointestinal and pulmonary tracts concluding with an examination of new murine models of mucosal inflammation. Epithelial cell function and mucosal homeostasis will also be examined. This is a subject that meshes well with the discussion of environmental factors in pulmonary inflammation being considered in the "sister" Symposium. Finally there will be presentations on homing of leukocytes to mucosal surfaces and the chemokine system. With this agenda, this Keystone Symposium will provide a keen examination of the major outstanding questions in the area of mucosal inflammation and will be an invaluable source of information for students and postdocs working in this area. It is expected that review of these topics will provide major insights into the mechanisms underlying mucosal inflammatory diseases such as inflammatory bowel disease and asthma.